Use hash map for O(1) key lookup in ConstantArrayType

`findKeyIndex` did O(k) linear scan per key, making `mergeWith` O(k²)
and `isKeysSupersetOf` O(k²). Add a lazily-built `keyIndexMap` that
maps key values to their indices for O(1) lookup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ondrejmirtes

src/Type/Constant/ConstantArrayType.php

@@ -94,6 +94,9 @@ class ConstantArrayType implements Type
 
 	private ?Type $iterableValueType = null;
 
+	/** @var array<int|string, int>|null */
+	private ?array $keyIndexMap = null;
+
 	/**
 	 * @api
 	 * @param list<ConstantIntegerType|ConstantStringType> $keyTypes
@@ -1805,15 +1808,17 @@ public function isKeysSupersetOf(self $otherArray): bool
 
 		$failOnDifferentValueType = $keyTypesCount !== $otherKeyTypesCount || $keyTypesCount < 2;
 
-		$keyTypes = $this->keyTypes;
+		$keyIndexMap = $this->getKeyIndexMap();
+		$otherKeyValues = [];
 
 		foreach ($otherArray->keyTypes as $j => $keyType) {
-			$i = self::findKeyIndex($keyType, $keyTypes);
+			$keyValue = $keyType->getValue();
+			$i = $keyIndexMap[$keyValue] ?? null;
 			if ($i === null) {
 				return false;
 			}
 
-			unset($keyTypes[$i]);
+			$otherKeyValues[$keyValue] = true;
 
 			$valueType = $this->valueTypes[$i];
 			$otherValueType = $otherArray->valueTypes[$j];
@@ -1828,7 +1833,10 @@ public function isKeysSupersetOf(self $otherArray): bool
 		}
 
 		$requiredKeyCount = 0;
-		foreach (array_keys($keyTypes) as $i) {
+		foreach ($this->keyTypes as $i => $keyType) {
+			if (isset($otherKeyValues[$keyType->getValue()])) {
+				continue;
+			}
 			if ($this->isOptionalKey($i)) {
 				continue;
 			}
@@ -1868,12 +1876,29 @@ public function mergeWith(self $otherArray): self
 		return $this->recreate($this->keyTypes, $valueTypes, $nextAutoIndexes, $optionalKeys, $this->isList->and($otherArray->isList));
 	}
 
+	/**
+	 * @return array<int|string, int>
+	 */
+	private function getKeyIndexMap(): array
+	{
+		if ($this->keyIndexMap !== null) {
+			return $this->keyIndexMap;
+		}
+
+		$map = [];
+		foreach ($this->keyTypes as $i => $keyType) {
+			$map[$keyType->getValue()] = $i;
+		}
+
+		return $this->keyIndexMap = $map;
+	}
+
 	/**
 	 * @param ConstantIntegerType|ConstantStringType $otherKeyType
 	 */
 	private function getKeyIndex($otherKeyType): ?int
 	{
-		return self::findKeyIndex($otherKeyType, $this->keyTypes);
+		return $this->getKeyIndexMap()[$otherKeyType->getValue()] ?? null;
 	}
 
 	/**